A polyvinyl alcohol (hereinafter sometimes referred to as “PVA”)-based resin is a water-soluble resin and has moisture absorbability. The PVA-based resin is typically stored and distributed in the state of a solid (e.g., powder or a granule). However, even in the case where the resin absorbs moisture in the course of its storage or distribution, when the resin is used, the resin is dissolved in water and used as an aqueous solution. Accordingly, the moisture absorption itself has not been perceived as a problem. That is, when the PVA-based resin absorbs moisture, blocking may occur, but the dissolution of the resin in water eliminates the blocking. Accordingly, only the prevention of water leakage is considered in a packaging bag to be used at the time of the sealing of the PVA-based resin, and hence a packaging bag made of polyethylene terephthalate has heretofore been used.
Such packaging bag is applied not only to an unmodified PVA-based resin but also to various modified PVA-based resins, and has been used for, for example, a PVA-based resin that contains a modified group having active hydrogen. The bag has been similarly used in the case of an acetoacetyl group-containing polyvinyl alcohol-based resin (hereinafter sometimes referred to as “acetoacetylated PVA-based resin”) disclosed in Patent Literature 1 that has high reactivity with a crosslinking agent and hence has been developed into various applications, or a polyvinyl alcohol-based resin containing a diacetone acrylamide structural unit (hereinafter referred to as “diacetone acrylamidated PVA-based resin”) disclosed in Patent Literature 2.